Question

Calculate the normal force for a 2 kg object at rest on an inclined surface, α=42 degrees

How much is the static coefficient of friction between the surface and the block

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My work:

N = mg*cos(θ)
N = (2kg)(9.8n/m^2)cos(42) = 14.57 N

F = µsN
µs = F/N
µs = (2*9.8)/14.57
µs = 19.6/14.57 = 1.345

I think I got the first part of the question right, but unsure about the second part if I switched the F and N since I had to calculate the normal force at rest for the 2 kg on a flat surface first.

Thanks in advance for any help.

Answer 1

Oops, the units for gravity are incorrect, it should me m/s^2.

Answer 2

F down slope = m g sin 42
= 2 * 9.8 * sin 42
= 13.1 Newtons down the slope
so
13.1 = mu m g cos 42

or
sin 42 = mu cos 42

mu = tan 42
mu = 0.900

At least 0.900
could be more